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jbd2: calculate statistics without holding j_state_lock and j_list_lock 

The two hottest locks, and thus the biggest scalability bottlenecks,
in the jbd2 layer, are the j_list_lock and j_state_lock.  This has
inspired some people to do some truly unnatural things[1].

[1] https://www.usenix.org/system/files/conference/fast14/fast14-paper_kang.pdf

We don't need to be holding both j_state_lock and j_list_lock while
calculating the journal statistics, so move those calculations to the
very end of jbd2_journal_commit_transaction.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Theodore Ts'o 2014-03-08 19:51:16 -05:00
parent 3469a32a1e
commit 42cf3452d5
1 changed files with 18 additions and 18 deletions
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36
fs/jbd2/commit.c
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@ -1083,24 +1083,7 @@ restart_loop:
atomic_read(&commit_transaction->t_handle_count);
trace_jbd2_run_stats(journal->j_fs_dev->bd_dev,
commit_transaction->t_tid, &stats.run);
/*
* Calculate overall stats
*/
spin_lock(&journal->j_history_lock);
journal->j_stats.ts_tid++;
if (commit_transaction->t_requested)
journal->j_stats.ts_requested++;
journal->j_stats.run.rs_wait += stats.run.rs_wait;
journal->j_stats.run.rs_request_delay += stats.run.rs_request_delay;
journal->j_stats.run.rs_running += stats.run.rs_running;
journal->j_stats.run.rs_locked += stats.run.rs_locked;
journal->j_stats.run.rs_flushing += stats.run.rs_flushing;
journal->j_stats.run.rs_logging += stats.run.rs_logging;
journal->j_stats.run.rs_handle_count += stats.run.rs_handle_count;
journal->j_stats.run.rs_blocks += stats.run.rs_blocks;
journal->j_stats.run.rs_blocks_logged += stats.run.rs_blocks_logged;
spin_unlock(&journal->j_history_lock);
stats.ts_requested = (commit_transaction->t_requested) ? 1 : 0;
commit_transaction->t_state = T_COMMIT_CALLBACK;
J_ASSERT(commit_transaction == journal->j_committing_transaction);
@ -1157,4 +1140,21 @@ restart_loop:
spin_unlock(&journal->j_list_lock);
write_unlock(&journal->j_state_lock);
wake_up(&journal->j_wait_done_commit);
/*
* Calculate overall stats
*/
spin_lock(&journal->j_history_lock);
journal->j_stats.ts_tid++;
journal->j_stats.ts_requested += stats.ts_requested;
journal->j_stats.run.rs_wait += stats.run.rs_wait;
journal->j_stats.run.rs_request_delay += stats.run.rs_request_delay;
journal->j_stats.run.rs_running += stats.run.rs_running;
journal->j_stats.run.rs_locked += stats.run.rs_locked;
journal->j_stats.run.rs_flushing += stats.run.rs_flushing;
journal->j_stats.run.rs_logging += stats.run.rs_logging;
journal->j_stats.run.rs_handle_count += stats.run.rs_handle_count;
journal->j_stats.run.rs_blocks += stats.run.rs_blocks;
journal->j_stats.run.rs_blocks_logged += stats.run.rs_blocks_logged;
spin_unlock(&journal->j_history_lock);
}